My characters have access to ammunition that is 50+ years old. They cannot acquire new ammunition. Thing is, according to my research, gunpowder degrades as much as 20 feet per second per year. For 50 years, that's 1,000 feet per second. The average speed of a bullet is 1,126 feet per second. That means that the ammunition they have, as it is right now, is practically useless. Is there a way to renew or "revitalize" aged gunpowder to make it more effective? Or, alternatively, what can be used as a decent substitute for gunpowder? I found this post about using very-very-very-very-super-finely ground-up matchheads as a gunpowder substitute, but the problem is that this method is very low-yield and time-consuming - my characters need a quick and expedient method to produce enough ammunition to sustain an army.